Question

How to do It??????????

Answer 1

given,
one opposite interior angle of a =40°
and exterior angle =120°
let, another interior opposite angle be x.
and third angle be y.

since sum of opposite interior angle=exterior angle.
so, 120=40+x
120-40=x
x=80°

now sum of all interior angles of a =180°
so, 40+80+y=180
120+y=180
y=180-120
60°

so, one angle of the =40°
other angle =80°
and third angle=60°

Answer 2

sum of 2 opposite interior angles is 120
so...40+x=120
x=80
and sum of all angles in a triangle is 180
so..40+80+y=180
120+y=180
y=60
so angles are 40,80,60